Unknown user account on os x

"So to summarize, this first image is a mockup of the results of an unknown input sequence caused by cleaning a keyboard on a system that was not shut down?"

-Yes, an input sequence while on "select account to login" screen, leads to the "group user icon" login screen (maybe "other" -can't recall), not originally shown as an option, and not present in Users& Groups Prefs.

"If this is typical for this display, then there’s a back button here somewhere, though that’s not shown in the mock-up."

-True, there is a "back" button to the initial "select user login screen".

Upgrading is not an option due to software incompatibility, BUT i don't think it is a Mavericks issue, rather an os x one (i.e a system account not a user one):

"We’ll review a few methods for advanced individuals to list all accounts, both user and system, on any Mac with any version of Mac OS X system software."

http://osxdaily.com/2016/07/05/list-user-accounts-command-line-mac/

***->Upgrading is not an option due to software incompatibility (software i use may have trouble running on a more recent version of os x)

Btw, thank you for your interest in my Question and i am sorry if the way i describe the "problem" is inadequate; i am not a native English speaker.

Ok. Thank you.

But have you ever heard that one can login with one of those system accounts by stroking a key combination at the "select user to login" screen?

As for the VM: Isn't that resource demanding? To run a 2nd OS + apps? Wouldn't it take a lot of (valuable) space on the ssd too?

My laptop is a MBP 13' late 2011. 10GB RAM, 276GB SSD (160GB free)

By "..have you ever heard that one can login with one of those system accounts..." i meant "..have you ever heard that one can get to a login screen for those accounts (by stroking a key combination at the 'select user to login' screen)", not actually logging into. Sorry for that. But how is this (the object/topic of this thread -if i got it right) a "network-connected system" problem?

External storage, unless over thunderbolt, would be a nightmare, plus it would restrain portability.

I really have no problem at all until now. The system runs seamlessly. It may seem that i am new user (level 1, 4 points XD ), but i actually have multiple macs since 2000, and a couple of amigas before that (there were a couple of years with no computer @all -97-00), and what i ve learned all these years is that hardware of an era plays better with software of that same era. Most of the new Os X (or MacOs) features wouldn't even be available on my machine, and i dont own an iphone so to miss the tighter integration. I am not sure how smooth the latest os would run on my MBP, or the problems that may occur due to old(er) hardware. I only make 2d graphics (literally i could use the machine for ages to do the job with no problem whatsoever) and do the usual internet stuff, i.e mail&browsing. It may be a time that the system would be unusable for the internet, maybe it would lack modern browser technologies, but by then i think even highsierra (last os i could go) would be about to become obsolete. So when that time comes, i may consider changing os and/or mac.

My post here wasn't about problem to be solved but rather a question for an oddity; that remains an oddity (to my).

Thank you so much for your time.

Hello Christopher,

I've checked that and the root is disabled. As i mentioned earlier in this thread, "It looks something like that **image**; (not sure for the "Other.." caption ― I created the image so to give a visual)"

Thank you

Hi,

just the 2 users + the guest, as i described in my original post